Last week we performed an installation on an employee's 1995 FJ80 rig. We installed both our new 3.12:1 low range gear set and also a center diff spool to enable part-time 4WD. We are having our new gears Made in Japan by Toyota's own gear cutter, the same gear cutter who makes our 4.70s!

The nice thing about this install is that it only requires the removal of the rear case (housing #2) and the rear extension (housing #3) housings. The transfer case itself remains attached to the transmission, and only the rear drive line needs to be disconnected from the unit. Here is a diagram of the rear components of the transfer case (photo copyright Toyota Motor Corp):

To begin, chock your wheels, shift your truck into low range and leave the transmission in neutral. It is important to shift the transfer case into low range so we won't have to reindex the low range actuator during reassembly. Remove the rear drive line and then set a jack beneath your transmission and unbolt the cross member to lower the drivetrain a few inches for a bit more room to play with. Drain the transfer case gear oil. The automatic transmission fluid does not need to be drained.

Next we disconnected accessories to the rear housings including the breather hose (atop housing #2), the plugs from the 4WD & neutral position switches, speedometer cable, and ground wire (all from housing #3).

Now we are ready to remove the rear extension housing. To do so, remove the 9 bolts holding housing #3 to housing #2, and then lightly tap on the housing with a soft mallet to break the silicon seal. These 9 bolts are not all the same length, so take note where each bolt is removed from. Also, two of the 9 bolts are installed into through-holes which require a thread sealant before reassembly. These two through-holes are circled in the image below. Their may be a trace amount of gear oil remaining so prepare for some to drip out once this seal is broken. The extension housing may now be set to the side.

Now we need to remove the #2 housing to get to our center differential and idler gear assemblies. To do this we first removed the 5 bolts holding the center diff retainer, and removed the retainer along with its adjusting shims (Note: As this is a differential, it uses tapered roller bearings that must be preloaded, just like the bearings on your third member carrier. This carrier uses shims instead of adjusting wheels to achieve this). Next, remove the 5-bolt case cover and remove the snap ring from the input shaft assembly. Below is a picture of the adjusting shim retainer (left) and the case cover (right). The rear case housing may now be removed. Again, take precautions for a trace amount of gear oil while removing this housing.

Next, in order to remove the low range gear assembly, we'll need to release the low range shift fork & rail from the transfer case, which is extracted with the low range assembly. We'll accomplish this in 3 steps:

3) Remove the torx bolt, and, using a magnet, extract the shift spring & ball being careful not to drop them.

The low range assembly is now ready for extraction. The low range shifter, now free to move, may be guided and rotated to allow the low range shift fork to clear from it, along with the center differential and idler gear's removal. The center differential, idler gear, and shift fork/rail will all be extracted as a complete assembly so be careful to hold the assembly together. They may be heavier than you expect so use care during extraction.

With the low range assembly removed, we are now ready to replace both the idler low speed gear and center differential low speed gear with our new Marlin Crawler CRAWLER GEARS!

This is a simple two step process: 1) Using a bearing splitter, press the idler gear away from the idler low speed gear and rear tapered roller bearing as pictured below. Tip: Take note of the orentiation of the shift hub by marking its top side, and support the shift hub from its bottom edge.

2) Replace the stock 19-tooth idler low speed gear with our 22-tooth Marlin Crawler idler low speed gear, and press the rear tapered roller bearing back onto the idler gear as pictured. Tip: Ensure you replace the shift hub in the same orientation as it was removed (the tapered edge should be facing the idler gear). Be sure to only apply pressure on the bearing's inner race, taking care not to contact the cage. If you simply press right across the bearing, you will damage the cage and destroy bearing.

Begin by removing the 12 bolts from the differential, and remove the differential's rear case. We won't have to worry about the rear tapered roller bearing since it it pressed onto & remains on the rear case. With the rear case removed, the pinion shaft, gears, and rear side gear are exposed. Remove the rear side gear and set it aside. The pinion shaft has two pinion gears and two thrust washers attached to it. Remove the shaft, gears, and shims, keeping them all together. Tip: Due to the pinion shaft's pin, it can only be installed in one orientation. You therefore do not need to mark the shims (so long as you keep everything together), however, it is good practice to mark which side of the pin is facing the rear cover. Tip: You must keep each thrust washer with their own pinion & side gears -- do not mix them up!

Flip the differential assembly over and remove the snap ring from the front drive gear. We are now ready to press the front tapered roller bearing from the front differential case.

Using a bearing splitter, press the shaft of the front differential case through the center of the front tapered roller bearing by supporting the assembly on the bottom side of the shift hub (similar to before). The front drive gear, roller bearing, high speed output gear, needle roller bearings and shift hub will all be removed during this process. Lastly, press off the high speed output gear bushing by supporting the low speed gear in your press. With the bushing removed, the clutch hub and low speed gear may be removed. Tip: Mark the top sides of both the shift hub and the clutch hub to ensure they are reinstalled properly. Tip: Remove the small shaft pin at this time to prevent misplacing it.

With the hub back on, apply grease onto the small shaft pin and install it back into the shaft (the grease will keep the pin from falling out). Before pressing the output gear bushing back on, it is important to note the alignment between the front case shaft pin and the slot on the output gear bushing. If the bushing is not properly aligned at the beginning of the pressing process, it will interfere with the shaft pin and you'll have to press it back off and start over. The best way to align the bushing is to align the two oiling holes before pressing the busing on, as shown in the following close up photos.

Once the output gear bushing has been pressed back on, reinstall all components: shift hub, needle roller bearings, and high speed output gear. Tip: Note your mark on the shift hub to ensure it is installed with the proper face facing upward, and align it to install over the three grooves of the clutch hub. Tip: Add grease to the needle bearings to hold them in place before installing the high speed output gear. Next, press the front tapered roller bearing back onto the front case shaft, making sure to only apply force through the inner race of the bearing (never press against the cage!) Finally, replace the front drive gear and its snap ring.

The last step is to reassemble the differential and reinstall the rear differential case.

Procedure for installing the factory center differential assembly:

Replace the pinion shaft with gears and shims onto the front case. The rear side gear may be placed atop the two pinion gears, or it may be placed inside the rear differential cover and lowered on top of the assembly.

Procedure for installing a center differential spool:

To install the center differential spool, transfer the rear tapered roller bearing to the new spool. Using a bearing splitter, capture the roller bearing by its inner race and press the rear differential case through its center. Press the bearing onto the spool making sure to only apply pressure through its inner race.

The pinion shaft, gears, thrust washers, rear side gear and pin are no longer required any may be discarded. The front side gear and its thrust washer however must be installed into the front differential case. It is required to support the front output shaft.

Final assembly procedure for all applications:

Now we are ready to install the 12 case bolts. Install all 12 bolts finger tight. Using a criss-cross tightening pattern, torque each bolt to 65 ft-lbs. Loosen all 12 bolts, and then retorque each bolt to 72 ft-lbs. Tip: A tightening pattern is not required for this final torque. The center differential, idler gear, and shift fork/rail can now be reassembled together. The final assembly will look similar to this:

Set the center differential assembly, idler gear assembly, and shift fork back together and you're done with the low range and differential assembly!

Before we can reinstall the assembly into the transfer case, we have to prepare the cases for the larger Marlin Crawler gears.

To do this, we'll first clearance the rear case. Using a die grinder or cut off wheel, remove part of the low range oil slinger as shown in the below image.

Additionally, a section of the housing will need to be clearanced as shown below. This section is circled green in the above image for reference.

Finally, the oil slinger located in the front case must also be clearanced in the same manner. Tip: Take extra precautions to protect both housings from debris. For the front case, we used a cardboard cut out to properly fit the housing to minimize the amount of exposure to the case. Afterwards, we sprayed the interior of the case with brake cleaner and used high pressure air to blast out any traces of debris.

Before installing the low range and differential assembly, degrease the flange sealing surface of the front case (housing #1). You'll have more room to clean and prepare the surfaces at this time. Also, add grease to the exposed rollers of all four tapered roller bearings. Tip: We chose to only grease the two forward-facing bearings so we wouldn't get grease all over our hands while inserting the assembly into the case. If you do this, be sure to add grease to the rear tapered bearings before installing the rear case (housing #2).

Holding the assembly together, install it back into the front transfer case housing. Remember any difficulties experienced during the extraction process to prepare for reassembly. If you take your time to ensure the assembly is held together properly, then the insertion process will be a breeze. Tip: As mentioned before, you may find the assembly heavy, so take care not to drop any components. Insert the front differential case over the front output shaft, and pay extra attention to the shift fork-to-inner-shift lever connection: The inner lever must be rotated into position to accept the shift fork, and then slowly rotated along with the insertion motion of the shift rail.

With the cases clearanced & mating surfaces degreased, we will do a dry test fit. Without using any sealant, attach the rear case (housing #2) to the front case. If you are able to mount it flush against the front case, then things are looking good. Install a few bolts around the case perimeter by hand. Don't force the cases together with the bolts; if the housings don't mount up effortlessly, then its likely you have not performed enough clearancing. (If this happens, it can be difficult to determine where interference is occurring. One method you may try is to apply a dab of grease where you've performed clearance modifications, and see where the grease is transferring across to the rear case. Then simply do more clearancing where the grease is being transferred.)

At this point, try to rotate the front drive line. You should know right away if the gears are interfering with the cases or not. If things are rotating freely, then reinstall the 5-bolt retainer plate with shim (this is the larger diameter shim). If you are still able to rotate the front drive line at this point, then congratulations, you've done sufficient clearancing! Remove the retainer plate, shims, and the rear case. If necessary, double check & degrease the mating surfaces of the cases, and then apply silicone to the rear case mating flange and install the rear case. Torque these bolts to 27 ft-lbs. (We recommend Ultra Gray Silicone) Pull or pry the input shaft assembly to expose the bearing snap ring groove, and install the snap ring. Tip: It is easiest to install this snap ring before tightening the housings together, which may make it difficult for the input shaft assembly to move. Reinstall the large diameter shim and the 5-bolt retainer plate. Torque these bolts to 28 ft-lbs. In the following image, the two bolts circled green have large washers, and the two bolt holes circled red are the two through-holes whose bolts will require thread sealer in the upcoming step.

Now it's finally time to install the rear extension housing! If your transfer case is equipped with a viscous coupler and you have installed the center differential spool, then you will no longer use the viscous coupler. Remove its c-clip and extract it from the output shaft.

Degrease both mating surfaces on the rear case (housing #2) and extension housing. Place the shim next to the idler gear assembly's rear tapered bearing (don't forget this!), apply silicone to the extension housing's mating surface, and install the extension housing. Remember to add thread sealant to the threads of the two bolts installed into the through-bolt holes! Torque these bolts to to 27 ft-lbs.

Degrease the mating surfaces of the case cover and the rear case (housing #2), apply silicone to the case cover's mating surface and install the case cover with its 5-bolts (torque to 27 ft-lbs). Apply thread sealant to the torx bolt (we use Hi-Tack Gasket Sealant made by LOCTITE), and install the shift rail detent ball, spring, and finally the torx bolt. Degrease the mating surfaces for the low range actuator, apply silicone to the actuator's mating surface, and install the actuator. Torque these bolts to 13 ft-lbs (156 in-lbs). The actuator does not need to be index because 1) the vehicle has already been shifted into low range, and 2) the shift linkage simply needs to be reconnected.

All that is left to do is to reattach the rear drive line, reconnect the crossmember, and add some gear oil! Tip: Before adding gear oil, it wouldn't hurt to ensure you can shift your transfer case between high and low ranges like normal. We recommend a GL5 75W-90 gear oil, and expect to use 1.5 quarts.

If you did not install the center differential spool, then the job is done!

If you did install the center differential spool, then there is one simple step left: Install the center diff lock switch (this switch is supplied with the spool). First, unscrew and remove the radio and climate control bezel to expose it's wiring harness. There will be an unused male plug with a female shorting-plug (or jumper-plug) attached to it (circled in the below image). This shorting-plug simply shorts a circuit that we'd rather like to operate manually. Unplug the shorting-plug, discard it, and then plug in the new Center Diff Lock switch in it's place. Install the new switch in place of the dummy switch cover, and then replace the bezel and you're done! Tip: It may be difficult to get the new switch to extend far enough to attach to the bezel. You've got two options: Reroute the plug's harness to gain more length, or tug gently on the plug's harness to gain another inch or so. With a little effort it will fit without any problems -- Toyota originally designed your truck with this feature, we just never got it in the States.

In closing, double check all bolts, inspect all areas serviced for any loose wires or hoses, and go out for a test drive. Ensure your shift lights are working properly and that your speedometer is functioning. If you installed the center differential spool, then be sure to NEVER engage or disengage your new center diff lock switch while the vehicle is moving.

If you have any questions at all, do not hesitate to give us a call toll free at (888) 94-CRAWL [888-942-7295]. Go out and start CRAWLING!

I'm not sure if this was the case in July, but the site now says they are closing out inventory of these gears. Get'em while you can!

marlincrawler.com said:

After almost a decade of selling our LC Crawler Gears, we have decided to shift our resources to new products and BLOW-OUT our remaining supply!
These are our exact same 100% made in Japan 3.12:1 LC gears that we've always sold but are now being offered at the lowest price ever, while supplies last!